Stencil paper



Patented Jan. 17, 1933 UNITED STATES PATENT OFFICE KENNETH W. CARE, OF OAK PARK, ILLINOIS, ASSIGNOR T DITTO, INCL, OFOHICAGO,

. ILLINOIS, A CORPORATION OF WEST VIRGINIA.

STENCIL PAPER N 0 Drawing.

My invention relates to stencil sheets, and more particularly to stencil sheets comprising a base material and a coating, the coating being such that it may be impressed and cut 3 by the type of a typewriting machine or by a sylus or similar agency.

i y invention also relates to a novel process by which new and improved stencil sheets may be produced.

:3 An object of my invention is to provide a stencil sheet which is cheap, durable and efiicicnt, and which may be used in a dry condition, will not crack under ordinary usage, is substantially unaffected by ordinary heat changes, is insoluble in ink, is strong, and is one the cut letters of which will last for im-' pressing an usually large number of copies.

The stencil of the present invention is distinguished from the stencil commonly used 55') by the fact that a chemical change toward insolubility is carried out in the film material after the stencil forming materials have been combined into the sheet support which is to be the stencil. The finished stencil is therefore a chemically processed stencil as distinguished from a physically processed stenoil. The base material before the chemical processing has characteristics of solubility or miscib lity for or in other material with :a which it may be as ciated in forming the stencil, but after the chemical reaction has taken place, these characteristics are destroyed, and a new substancewith new characteristics is produced. In other words, in spite of the fact that. soluble materials may exist in the stencil body, the desired insoluble character of the stencil is brought about both by choice of material and treatment of material. The stencil of. the present invention may have a film or coating which is not a single chemical composition, but rather a physical mixture, one component of which is the insoluble base which characterizes the invent on. Although other stencils are also physical mixtures, the manner in which their con,- stituents are associated is to be distinguished from the manner in which the constituents of my stencil are associated. The fact that the base is insoluble prevents deleterious at- Application filed September 29, 1926. Serial no. 138,572.

tack on an ink-soluble constituent, especially in the body of the stencil. The insoluble base protects the soluble components, whereas a partially soluble base would permit removal of the base as well'as other more soluble constituents. Accordingly, then, in spite of the fact that the present invention permits the formation of a stencil comprising mixed ingredients, some of which may be soluble in inks, the manner in which the insoluble component is produced in situ, leads to the formation of a physical protection for the other, constituents that may be soluble.

The principle involved in the formation of this type of stencil sheet is to provide a base material such as, for instance, a paper having long loosely associated fibers, preferably Yoshino paper, and treating this paper with a coating having three general properties, which are: first, insolubility in inks and ordinarv solvents encountered in its use; secondly, flexibility so as to maintain the coated paper flexible; and, thirdly, capability of being cut by contacting type or by a stylus in a manner to displace the coating material from that portion engaged by the cutting agency. In preparing the coating, the selection of a main ingredient which has as many of the above stated properties as possible'is preferable. I have selected as a main ingredient for my coating any one of a group of'substances known as phenol condensation products which are artificial resins or resinoids in form and which can be rendered insoluble in most substances such as in the ink used in reproducing copies. I preferably select a part cular phenol condensation product in the form of a varnish and as set forth in the patent toByck, No. 1,590,079, issued June 22, 1926. for the reason that this varnish has the additional property of being flexible thereby embodying in this one substance two of the three properties necessary for a stencil sheet coating, An inspection of this patent will show that the resin is characterized by first reacting phenol with tung oil and subsequently reacting the product resulting therefrom with a methylene carrying "substance, such as for instance, formaldehyde. The resin in many ways, is quite like the usual type of potentially reactive phenol formalde hyde resins, but it is unique in that it is extremely flexible due to the fact that the phenol is reacted with tung oil prior to the subsequent reaction with the methylene groups. Phenol condensation products are prepared from phenols reacting with other substances, and the properties of the final product depend upon the proportions and the particular kind of phenol and reacting substance selected for the production of the finished product. The varnish above mentioned is found to possess great flexibility as well as being unaffected by the ink, and is, therefore, particularly suited for use as the main ingredient of my coating material.

It is to be understood that the phenol condensation product itself is a resinoid and the varnish spoke-11 of is a solution of that resin, the solvent being largely toluol, benzol or ethyl alcohol, or various mixtures of these, the toluol being that preferred perhaps mixed with a little ethyl alcohol. During the process of producing the resinoid product, it is necessary in order to effect the proper chcm ical change between the constituent parts to subject the product to a heat treatment. This heating operation effects the change in the substance which produces its insolubility, the substance in an intermediate stage having the same physical appearance as the finished product but being quite soluble in the above named solvents. It is by virtue of this fact that these products are extremely serviceable for my use in that a solution may be made from the resinoid in this intermediate stage so as to form varnishes or the like to be applied as desired and subsequently baked to render them substantially insoluble. The term phenol condensation product is properly applied to the final insoluble product which has been completely baked, but for convenience in explanation and to aid in a better understanding of this invention. the term phenol condensation product will be applied to the resinoid used to form my coating solution which is subsequently baked after being applied to the Yoshino sheets.

By the term resinoid as used in this specification, I mean a resin which is completely reacted as by heat treating a potentially reactive resin, as distinguished from a resin which is permanently soluble and fusible. It is well known in the art of phenol condensation products that as proportions of phenol to the reacting substance, such as for instance a substance containing methylene groups, differ, that different results and products will be had and that permanently soluble and fusible products can be produced which cannot be changed by heat treatment alone, and that products known as potentially reactive products can also be formed which products are capable by heat treatment alone of undergoing a further reaction which renders them substantially insoluble and infusible. It is the artificial resins which are produced by reacting, such as by heat treating a potentially reactive resin and are substantially insoluble and infusible that are well known in the art as rcsinoids as distinguished from resins. The permanently soluble and fusible resins are known as artificial resins and are in a general way considered as substitutes for natural resins.

.The other substances in addition to the bakelite resin used in my coating are employed for the purpose of bestowing upon the resinoid the property of being impressionable by the cutting type or stylus when in the form of a coating on a sheet. Various substances have been selected as serviceable in this capacity, the main properties of which are the same. It is found desirable to provide a shortening agent and a softening or tempering agent. The shortening agent operates to weaken the resinoid; that is, render it less tough so that it may be more readily cut by the cutting agency, and the softening agent is preferably an oil or fat or a mixture of two or each of these so that the softening ingredient will lend to the combination of substances some of their properties to effect the properties of the whole. I have found that the shortening agent may be either a metallic soap, such as aluminum stearate, or a wax such as China wax, par-affine wax or a tallow such as Japan wax, Chinese tallow or a regular animal tallow, and also that zinc oxide, barium sulphate, carbon, lithopones, and carbonates such magnesium carbonate, serve well in this capacity. Of these last named shorteners, barium sulphate is found to be very desirable in its effect with the phenolcondensation product. When some of the insoluble shorteners are used, an emulsion is formed instead of a solution. the result being the same in either case, namely, the production of a homogeneous coating.

For the softening or tempering agent, almost any oil or fat will serve, the selection found preferable for my use being a mixture of dibutylphthalate and neats-foot oil, or in some instances, neats-foot oil alone or hydrogenated cottonseed oil or any other fatty oil.

For my solvent or thinner, it is only necessary to have some common solvent for all of the ingredients or to select solvents for the alcohol or toluol, for instance, and upon be-- ing baked to a predetermined extent is rendered substantially insoluble in these same solvents. This property of potentially reactive phenol condensation products renders them particularly useful in the formation of stencil sheets as described for the reason that a solution may be formed in this prehaked or reactive condition so as to effect a homogeneous mass of the ingredients, the solution applied to the sheet, the same heat treated to drive off the solvent and to render the final product substantially insoluble. It is to be understood that the heat treatment of the coating solution, which coating comprises a mixture of the resinoid, a shortener and softening substances, acts to further a reaction between the constituents of the resin to produce the property of insolubility similar to that which would be accomplished by heat treatment to the resin alone.

Various combinations of the substances have been selected as the ingredients of my coating material, one combination comprising the resinoid varnish, aluminum stearate, wax and a softening agent including dibutylphthalate and neats-foot oil. A second combination of substances is similar to that above given with the exception that parafiine is dispensed with. A third selection of substances and proportions which is found highly desirable employs neats-footoil or any other fatty oil softener together with the other ingredients eliminating the use of dibutylphthalate. To all of these mixtures before they are finally prepared a coloring matter such as Victoria blue base or other suitable coloring matter is added, serving to render the coating opaque so that the cut letters of the stencil which reveal the white paper fibers may be readily seen by the contrast.

I will now describe the method of preparing a stencil sheet which is found to serve well for the purpose set forth but which is merely one preferred embodiment of my invention. To prepare the coating. eight parts by weight of 124 F. melting point paraffiue is heated to its liquid state, and while maintained in liquid state twelve parts of aluminum stearate, seven parts of neats-foot oil and fourteen parts ofdibutylphthalalate are added. Coloring matter is dissolved in a thinner which is preferably thirty parts by weight of a mixture of alcohols. benzols, or esters. or any suitable mixture of these, but which by way of example may be toluol and ethyl or butyl alcohol mixed in proportions of twenty to twenty-five parts and the mixture added to the melted paraiiine. This mixture is kept at a temperature of about 45 to 50 centigrade. Sixteen parts by weight of the resinoid varnish, containing substantially 45% of the solid resinoid. is then added and the product stirred. This coating solution being prepared, the Yoshino paper is then coated in the usual way, the sheets being immersed or floated upon the coating bath or liquid. Vhen the sheet has been thoroughly covered with the solution, it is drawn across a straight edge or wire to remove the excess of the solution and then hung up to dry, the drying operation serving to volatilize part of the solvent. After the drying operation, the sheet is placed in an oven, the temperature of which is between 90 and 150 C., but preferably 140 centigradefand baked for a period of thirty to sixty minutes. After baking, the sheet is removed and cooled, at which time the stickiness present under the heat treatment disappears, the product being at this time substantially insoluble by virtue of the reaction produced by the heat treatment between the constituent parts of the potentially reactive phenol condensation product.

In the form of my improved coating that dispenses with the paraifine, the oils are mixed together to which is added the aluminum stearate. These substances are then taken into solution by the addition of an appropriate amount of thinner and the solution finally added to the varnish. In this instance, the proportions will be sixteen parts by weight of a 45% resinoid varnish XH871, sixteen parts of aluminum stearate, ten parts of neats-foot oil, ten parts of dibutylphthalate, thirty parts of thinner or solvent.

In another composition, I found that mixing the following ingredients in the proportions indicated it is possible to eliminate the dibutylphthalate. This solution is as follows: sixteen parts of resinoid varnish, fourteen parts of aluminum stearate, thirteen parts of hydrogenated cottonseed oil, and twenty-five parts thinner or solvent.

It has been found that Yoshino paper coated and treated in the above indicated manner forms a greatly improved stencil sheet. The coating as prepared is quite insoluble in oils and inks and yet is of such a character that it may be readily pushed aside to expose the fibers with av small portion thereof pushed through the fibers onto an absorbent sheet when it is being cut, so as to form very accurate letters. It was also found that a sheet thus prepared when out is very durable and will withstand the wear of a large number of reproductions without causing blur or imperfect letters. Furthermore, the sheet is unaffected by weather conditions, remaining in good workable condition at all times and is not subject to being dried and hardened by exposure to the atmosphere, nor is it subject to being cracked in a manner to pass ink when it, is creased or folded in ordinary usage.

It is of course to be understood that the invention is not limited to the present disclosure and that various changes may be made in the composition. The important features of the invention to be considered are the chemical formation of an insoluble base, such as a resin, in situ, the combination with the baseforming material prior to the chemical formation of the base of the modifying agents.

I claim:

1. A stencil sheet comprising paper of loose, open texture. and a coating including a reacted potentially reactive phenol condensation product, and aluminum stearate.

2. A stencil-sheet comprising paper of loose. open texture, and a coating including a homogeneous mixture of a reacted potentially reactive phenol condensation product, aluminum stearate, and a softening agent.

3. A stencil sheet comprising a paper of loose, open texture, and a coating including a reacted potentially reactive phenol condensation product,- and a Wax.

a. A stencil sheet comprising paper of loose, open texture, and a coating including a reacted potentially reactive phenol condensation product, and dibutylphthalate.

5. A stencil sheet comprising paper of loose, open texture, and a coating including a reacted potentially reactive phenol condensation product, and neats-foot oil.

6. A stencil sheet comprising a paper of loose, open texture, and a coating including an insoluble infusible artificial resin.

7. A stencil sheet comprising a paper of loose, open texture, and a coating including a reacted potentially reactive phenol condensation product, and a metallic soap.

8. The process of forming stencil sheets consisting in dissolving a potentially reactive phenol condensation product and adding to the solution a second solution comprising a shortening agent, a softener, and a solvent, and coating paper with said solution.

9. The process consisting in coating a paper of loose, open texture with a solution ineluding a potentially reactive phenol eondensation product. a'shortening agent, and a softener, then drying and heat treating the coated paper at a temperature of substantially 140 C. to 150 C. until substan tially insoluble in inks.

10. The process of forming stencil sheets consisting in coating paper of loose, open texture with a coating material including a. potentially reactive phenol condensation product.

11. A method of making insoluble stencils which comprises baking insoluble-resinforming substance with a resin-softening agent whereby to form a resin in situ embodying the softening agent.

12. The process of forming a stencil sheet coating material which includes the step of dissolying a potentially reactive phenol condensation product, a shortening agent, and a softener in a common solvent.

13. The process of forming stencil sheets consistin in coating a paper of loose, open texture, with a substance including a poten-v tially reactive phenol condensation product and then heat treating the coated paper an amount effected by a temperature of substantially one hundred and forty degrees C. to one hundred and fifty degrees C. from thirty to sixty minutes.

14. A stencil coating having as a base a synthetic resin of the phenol condensation type which is finally reacted and incapable of polymerization.

15. The method of making stencils which consists in producing a solution of insolublecoating-forming substance and a modifying agent, coating a sheet With said solution, and then heat treating the coated sheet whereby to form an insoluble coating in situ on said sheet embodying said modifying agent.

16. A stencil sheet comprising a foraminous base material and a coating including a flexible, insoluble, infusible artificial resin.

17. A stencil sheet comprising a foraminous base material and a coating including an artificial resin produced from a phenolic body, tung oil d methylene carrying sub stances.

Signed at Chicago, Illinois, this 25th day of September, 1926.

KENNETH W. CARR. 

